This is the Enigmatic Incarnation nonsense you're here for- play etb enchantments for value, then sack them for a toolbox of even more value. All your creatures revolve around answering anything your opponent plays in the most elegant fashion possible, and because Enigmatic Incarnation pulls them from enchantments, that skyclave apparition you wanted to play now costs 2 mana and cantrips itself. 

This deck in particular focuses really heavily on the opening curve. We run a lot of early mana and removal spells to maximize nut draws, because we really need those to survive against aggro decks. What does that mean? Well, the dream hands are

(x+Wolfwillow Haven+Enigmatic Incarnation),

(x+Llanowar Elves+3cmc enchantment+Enigmatic Incarnation),

(x+Trial of Ambition+3cmc enchantment+Enigmatic Incarnation), and

(x+Omen of the Sea+Oath of Kaya+Enigmatic Incarnation).

As you can see, there's a lot of dream hands, and that's exactly what you need to actually survive the early onslaught. After Incarnation comes down, the value engine is so powerful that you don't really care anymore. Any card in your deck is probably the best card in your deck, plus cantrip.

Here's a card by card breakdown:

Llanowar Elves: Unfortunately, we put these in the deck. Paradise Druid, while much nicer for mana fixing, doesn't fit into the curve (you want to be going elves>3 drop> incarnation), and so we need these. Goose only works once, so it's elves or bust. A necessary evil. Turns a lot of slow hands into extremely good ones.

Bloodchief's Thirst: Cheap removal, you really want it so don't get run over before you can play an incarnation. This instead of Fatal Push because it's really hard to activate revolt outside of right after Incarnation, and instant speed isn't a huge priority. The flexibility to go after big creatures and planeswalkers is sometimes nice.

Omen of the Sea: Bread and butter of the deck, we'd probably run 6 (or even 8) copies of it if we could. It's the best cantrip 2cmc enchantment there is, digs you deeper towards incarnation, can be sacrificed to scry in a pinch. 

Urban Utopia: Worse Omen of the Sea. Here because I wanted more cantripping enchantments and out of the three main ones available (Lithoform Blight and Confounding Conundrum too), mana fixing is probably the most relevant. Conundrum might stop an Uro land, so it's worth consideration. 

Wolfwillow Haven: Enchantment based ramp, mostly here for the opening pattern of x, Wolfwillow Haven, Enigmatic Incarnation sack haven for a 3 drop.

Trial of Ambition: Our 2 cmc removal of choice. It's a bit greedy, but usually the sacrifice is good enough to stall for time before you can stabilize. Other options are Baffling End for the ability to target at the cost of making a 3/3 when you inevitably sacrifice it, and the trusty Heartless Act.

Oath of Kaya: The dream card against any type of aggro matchup, lightning helix and a 4-drop. Only 3 copies because it's effectively a blank against any non-creature matchup, and sacrificing it to incarnation is pretty eh if you don't get value on etb.

Treacherous Blessing: What more can you ask for than 3 cards? Incredibly good when it's good, but it will not hesitate to kill you. Only one because it's so brutal when life matters. 

Disinformation Campaign: Treacherous Blessing, but it won't kill you. It's two card advantage, its backbreaking against slower decks, you'll appreciate it when you need it.

Skyclave Apparition: You already know why this card is great. It's one of the best pulls out of a 2-cmc enchantment, and the only reason we don't run more is the 1WW casting cost is brutal to play on curve.

Deputy of Detention: Easier to cast apparition a lot of the times, but also can hit tokens, multiple creatures, and high-cmc things. Also an all-star.

Knight of Autumn: It's a toolbox inside a toolbox! Incredible way to tutor up artifact and enchantment destruction, absolutely tears mud to pieces, can be an emergency stabilizer with lifegain, almost never dead in hand. Two in the sideboard because there are just some matchups where you can never get enough. Also blows up Grafdigger's Cage.

Uro, Titan of Nature's Wrath: It's uro. Can't have simic colors without him. Don't need the ramp all that much, but a recursive threat that draws cards and gains life? Deal.

Renegade Rallier: If you're not under pressure, this is the go-to card. Almost always fetches back the enchantment you just sacked. The dream is sack Omen of the Sea, pull Rallier that replays Omen for another scry 2 and draw and refuel your next incarnation. Only one copy because revolt really is brutal to activate, especially if you can't do it at instant speed.

Glasspool Mimic: There's a lot of one-ofs in the deck that we wouldn't mind tutoring more of. Mimic does the job just fine for that. Super low opportunity cost because it's also a land.

Archon of Emeria: Our single silver bullet in the 3 cmc slot. Turns off neostorm and paradox engine decks entirely, is a pain for a lot of decks to play into, and our deck doesn't mind being limited to a single spell a turn because incarnation basically turns our single spell into two already.

Enigmatic Incarnation: It's the whole point of the deck, silly. If you draw two of them, you can sacrifice one to get a 5-drop, or even sacrifice both at the same time to get two 5-drops.

Ravenous Chupacabra: Understatted, yeah. It's the only hard murder on a creature though, and that's real nice when you need it.

Hostage Taker: Basically Chupacabra but fancier. Can nab artifacts, you can replay whatever you steal, and has a bit of a better body. 

Shifting Ceratops: An actual threat. 5/4 is a sizable body, protection from blue isn't bad at all, and can have keywords when you need it. There's an argument here to run Questing Beast instead.

Archon of Sun's Grace: Fancy stabilizer, can get out of control real fast with Yorion nonsense, has lots of lifegain and chump blockers. Admittedly, it's a little better on paper than in practice, you're only really playing a single enchantment per turn. Still, it's quite good as a one-of.

Archon of Absolution: Another fancy stabilizer, puts a halt to a lot of go-wide strategies. Goblins and elves particularly need to throw a lot of mana to fight through it.

Yasharn, Implacable Earth: Silver bullet #2, you all know and love the hateboar himself. There's an extra copy of a plains and forest just for him, but usually you only get 1 land by the time he comes down. That's fine, he's really only here to turn off sacrifice abilities. Important to note: Yasharn doesn't turn off incarnation because it's not an activated ability, so you can pull him without fear.

Yorion, Sky Nomad: A single copy in the main deck just in case you end up with multiple incarnations. When Yorion's good, it's really good. We have tons of etb effects, and if any enchantments are still around, they'll double dip too. 

Cataclysmic Gearhulk: Oh boy, this one's a doozy. Not sure if it belongs in the deck, but it's certainly nice knowing you have access to a boardwipe when you need it. Lets you keep incarnation, which is nice. If we were running ECD, this would definitely be replaced by Massacre Wurm.

As for the sideboard:

Disdainful Stroke: Shores up your holes against mud and sultai, bring some in against goblins, it's nice to have counter magic. 

Mystical Dispute: Did I mention shoring up holes against sultai? We need all the help we can get there. Also pushes through all the various control shells, be it dimir or azorius or whatnot.

Sparkhunter Masticore: You'll know when you need this. If they've got planeswalkers, make sure they no longer have planeswalkers.

Knight of Autumn: Sometimes, it's a full playset of KoA kind of game. Mud hates it when you can 2 for 1 all of their cards. In game 3 you're often bringing all of them for the cage they inevitably board in.

Trial of Ambition: The rest are here just for extra creature hate. 

Destiny Spinner: A nice ace against counterspells, extra useful after sideboarding to stop all the new mystical disputes that will show up. Can be sacrificed to incarnation.

Yorion, Sky Nomad: He's our companion!

Cards you might consider:

History of Benalia: It's another 3 cmc enchantment. Making knights is nice, and it's a ton of value and can stall for two turns on its own. We don't run it because 1WW is still brutal (see Skyclave Apparition) and far too often we sack it after its only made one knight.

Elspeth's Nightmare: Definitely a better card in Standard than Historic. If you get all the modes in, the kill-duress-turn into a 4 drop, it's incredible, but it's pretty diffcult to consistently find a creature with 2 power or less. Competing with Oath of Kaya is pretty difficult.

Birth of Meletis: Lets you hit more lands, makes a wall, heals you. It's nice, but forces us to run way more plains than I'm comfortable with. Often I'd rather just dig with Omen of the Sea.

Lithoform Blight/Confounding Conundrum: I've already talked about both of these, it's pretty much up to personal preference which of the 3 between them and Urban Utopia you prefer. For me, it's Urban Utopia.

Mantle of the Wolf: It's History of Benalia without any of its problems, for the price of one more mana. Could be cute with Tolsimir, but for now it's too expensive and the deck is focused around 2 and 3 mana enchantments.

Leyline of Abundance/Leyline of the Void: This is getting into some big jank territory. If you can get it in your opening hand, you can turn it into a free 5 drop. Too janky for me, but it's hilarious when it goes off. Leyline of Abundance can make Llanowar Elves accelerate Incarnation out on turn 2 for a 5-drop.

Setessan Champion: Crazy card draw when she goes off. Too win-more for me, I usually would rather pull a Renegade Rallier for the instant card draw.

Vengeful Rebel: It's incredibly good against creature strategies. Kill something, leave a 3/2 blocker that doesn't give them back a token when it dies. No revolt means it's a vanilla 3/2 for 3 though, so it's spooky to run.

Elite Guardmage: I really hate this card. It feels so understatted. A 4 mana 2/3 that draws a card and heals 3? Meh.

Atris, Oracle of Half-Truths: Elite Guardmage but weird. Sees more cards and can draw more cards, but no lifegain or flying. Maybe if we ran thassa he would make the cut.

Kaervek, the Spiteful: Silver bullet, he comes down and blanks anything with 1 toughness. This could mean disabling Krenko or locking elves out of the game if you can kill their lords. Unfortunate nonbo with Llanowar Elves, and might be too narrow to deserve a slot.

Thassa, Deep-Dwelling: This is kind of neat. Being able to get free etb effects each turn is nice, and she counts as an enchantment creature, so we can sacrifice her to Incarnation in a pinch. We don't run her because unlike playing her from hand, when you tutor her out, it's already end step, so we don't get any Thassa triggers that turn. Don't like tutoring a 4-mana do nothing spell very often. 

Lurrus of the Dream-Den: Neat as a 1-of to recur your cheap enchantments (read: omen of the sea). Kind of outshone by Renegade Rallier, although I would consider putting a copy of Lurrus in if you have the room.

Dryad of the Ilysian Grove: Mainly here because it's an enchantment creature, so you can both tutor into it and sacrifice it for something else. Fixes all our mana perfectly, which is sometimes a godsend. The ramp is neat, but not super useful. Just overall doesn't do enough to make the cut.

Demonic Pact: Oh man, this card is crazy. It's like Treacherous Blessing on steroids. Potentially a 5 for 1 that can be turned into a 5 drop, but that last bit of text, the lose the game bit, is... it's game losing. I'd totally run it if I had the balls. 

Yarok, the Desecrated & Tolsimir, Friend to Wolves: I consider these two a package. If you want to fit them in, take out Yorion and Gearhulk and they slot in nicely. The wombo-combo is getting a second incarnation on the board, then sacrificing both of them for Yarok and then Tolsimir. Yarok doubles Tolsimir's triggers, creating two wolves, and then each of those wolves fights twice and gains you 3 life twice, for a total of 4 fight triggers and 12 life. Potentially game-winning on the spot, but otherwise, they're pretty mediocre cards on their own. I prefer the flexibility of being able to pull one creature at a time. Certainly a consideration though.

Cavalier of Dawn: Ok, Cavalier has some crazy synergy with this deck. Tutorable removal, recurs any enchantment you want for any card in your deck you want, great stats. Why don't we play him? 2WWW. Nope. You'll never cast him from hand.

Thragtusk: Kind of neat, but for a whole Incarnation, I want more than 5 life and some bodies. I'd consider it with Thassa or in a shell with more 4 drop enchantments.

Klothys, God of Destiny: I'd totally run her if I could, but 5c is brutal. The mana base is messy enough as it is. Graveyard hate, lifegain, burn, and an enchantment creature that can be sacked to incarnation? Sign me up!

Elspeth Conquers Death: This is actually interesting. Most incarnation decks run the ECD+Dream Trawler+Kogla package, but we don't. Why? Too high on the curve, we already have tons of ways to answer everything already. If we can survive into the midgame and establish an incarnation to sacrifice ECD to, we're probably already winning. No need to run cards that mess up your opening hands to do it.

Niv-Mizzet Reborn: The ultimate jank addition to the deck. If you want to make a 5c incarnation pile with Niv, go on ahead. It'll be crazy. I don't think it's very easy anymore without fires, and it'll be a totally different deck, but man, it'll be fun.

Etrata, the Silencer: No. Don't. There is such thing as too much jank.

What could be worked on? Well, the toolbox is still quite messy. There are a lot of good creatures out there, and certainly more room for experimentation. You can try pivot the deck to a higher curve, running ECD and 6 drops to go way over the top. Possibly most importantly, the manabase is a mess. I'm particularly bad at crafting manabases, and while this works alright, its by no means optimal. Someone better than me can work the kinks out there.

The deck is filled with decision points and is a blast to play, so I recommend you give it a shot. How competitive is it? Not all the way down in ditherly jankville, but I don't know if I'd tier it. Most importantly, it's almost (or even more) fun to build than to play. Finding all the right cards to put in is just as much the game as actually playing them. If that sounds like your thing, then go for it!